Could a carrier make the job easier?
3
Biodegradable materials
Paper bags degrade quite quickly. Your class can investigate this by burying paper different sorts of paper (taken from different paper bags) and seeing what happens to them over time. They will need to remove the covering earth carefully, make observations, and then replace the earth carefully.
There are several of decisions to make in setting up this investigation - how deep should the paper be buried? Should it be spread out flat or scrunched up? How often should you look at it? An interesting way to make observations would be to take a digital photo of the paper each time it was uncovered and then put the photos into a PowerPoint sequence, which would give an overview of the degradation.
Shoppers in Britain are estimated to use up to 20 billion plastic carrier bags a year. 
Only one in every 200 is recycled and each takes about 100 years to degrade. So there is a lot of interest in making plastic bags that biodegrade. The country's first degradable carrier bag is being provided at Co-op supermarkets. The bag, available free of charge from Monday, will disintegrate to practically nothing within three years, it is claimed. Co-op states that the new degradable bag will be strong and reusable, with a special additive, which starts the degrading process after 18 months.